Combination electronic and air-column actuated stethoscope



D. C- KEESEE Nam 1, 1m

COMBINATION ELECTRONIC AND AIR-COLUMN ACTUATED STETHOSCOPE Filed July 5, 1967 2 Sheets-Sheet 1 FIG.3

. INVENTOR DANIEL C. KEESEE United States Patent 3,539,724 COMBINATION ELECTRONIC AND AIR-COLUMN ACTUATED STETHOSCOPE Daniel C. Keesee, 20 Midwood Drive, Florham Park, NJ. 07936 Filed July 3, 1967, Ser. No. 654,312 Int. Cl. H04r 23/00 US. Cl. 179-1 8 Claims ABSTRACT OF THE DISCLOSURE An air-column-actuated combination electronic and standard stethoscope having a unique valve means which permits virtually instantaneous transfer from one mode of operation to the other. A transistorized amplified circuit accommodates an input jack whereby a patients present heartbeat may be compared with a known standard including the patients previous condition such as by making a recording thereof. The stethoscope permits monitoring of the patients condition from a central station and is useful as a teaching device.

It has been known for many years to construct standard stethoscopes which are actuated by a column of air. It is also known to use electrical amplification in making an electronic stethoscope. However, it has never heretofore been feasible to combine an air-column actuated stethoscope with an electronic stethoscope. Nor has it been possible in a single device to be able to switch substantially instantaneously from one form of stethoscope to the other.

It is recognized that the sounds produced in the earpieces of an electronic stethoscope differ from actuated stethoscope. By having substantially instantaneous interplay between the two, it is possible to become familiar with the differences in sound quite readily.

The subject invention also makes it possible to convert a standard stethoscope into a combination electronic and standard stethoscope merely by inserting an amplifier circuit and the valve means of the present invention at a convenient place in the air column between the conventional pickup head and the Y connection leading to the conventional earpieces. Thus the physician may continue to use components of his conventional stethoscope to which he has become accustomed.

The electronic stethoscope has diagnostic advantages for all and especially for the hard-of-hearing doctor. In cardiology, distant low-pitched heart tones and murmurs may be amplified for easy detection. In obstetrics and gynecology, it becomes possible to detect the frequently indistinct fetal heartbeat caused by obesity or position of the fetus. In diseases of the chest, it is frequently difficult to hear pulmonary tones especially when chronic emphysema or obesity is present. Amplification makes audible conditions which otherwise might not be discovered until a much later date.

A significant advantage of the electronic stethoscope is that the form of output terminal connections permits recording of the heart sounds on tape, disc, brush, or other type devices for permanent records and case histories.

These and other advantages of the present invention will become readily apparent upon reference to the following detailed description and drawings wherein:

FIG. 1 is a perspective view, drawn on a reduced scale, of the stethoscope of the present invention.

FIG. 2 is a cross sectional view of the housing which receives the electrical amplifier circuit and valve means of the present invention.

FIG. 3 is a fragmentary cross sectional view taken along line 3-3 of FIG. 2.

3,539,724 Patented Nov. 10, 1970 column is provided by means of flexible hose 14 which leads to a housing, indicated generally at 16, for retention 'of an electrical amplifier circuit and valve means to be described hereinafter in greater detail.

Extending from housing 16 is a conventional flexible coupling or hose 18 which incorporates a conventional Y connector to extension pieces 20, 22 at the ends of which are located a pair of earpieces 24, 26. For convenience in carrying the stethoscope around the neck, a strap 28 may be attached to housing 16.

Referring now to FIGS. 2, 3 and 4, there is illustrated a cross sectional view of housing 16 within which is received the electrical amplifier circuit indicated generally at 30 and the valve means indicated generally at 32. A turning knob 33 external to the housing 16 is carried on a shaft 36, preferably made of brass, which passes through a drilled hole in the wall of housing 16 and is affixed to a rotatable cylindrical core 38 by means of a set screw 40 within a fixed outer sleeve member 42.

A tube 44 is frictionally received in a first aperture in fixed outer sleeve member 42 and passes through a drilled hole in the bottom of housing 16 so as to frictionally receive the end of flexible hose 14. The core 38 of the valve means 32 is provided with a first pasageway 46 which establishes direct communication between a first air column within the flexible hose 14 with a second air column defined by a tube 52 and flexible hose 18. The fixed outer sleeve member 42 is provided with a second aperture into which is frictionally inserted a tube 50. Any suitable epoxy adhesive or sealant may be used to insure that tube 50 and other tubes used in the valve construction provide an airtight closure. Tube 52 is inserted through a third aperture in outer sleeve 42 and is in axial alignment with the air column leading into the base of housing 16. A fourth aperture in the outer sleeve 42 receives a tube 54 which communicates acoustically with the output of loudspeaker 60 of the amplifier circuit. With the valve means in the position shown in FIG. 4, a passageway 57 in core 38 redirects the amplified physiological sound from tube 54 back into the second air column in tube 52 and flexible coupling 18. The passageway 57 is preferably ball milled into core 38.

It is most important that the valve bemade with considerable precision. Thus all portions of the surface of core 38 must be free from tool marks as well as all internal passageways so that there is no obstruction to the acoustical efficiency of the device. It is noted that tube 50 leads to a cone 56 into which is taped a second acoustical transducer in the form of a microphone 58. This second acoustical transducer is electrically located in the first input stage of the transistorized electrical amplifier circuit as will be described more fully hereinafter.

The loudspeaker 60 illustrated in FIGS. 2 and 4 is preferably a high impedance device which may be, for example, a Telex RTY04 having an impedance in the order of 2000 ohms. A 30 volt DC battery is indicated at 62 in FIGS. 2 and 4.

Referring now to FIG. 5, there is illustrated one form of electrical amplifier that has proven to be satisfactory for use in the practice of the present invention. It is to be understood that any suitable amplifying circuit may be substituted for the illustrated circuit for use with this invention.

FIG. discloses battery 62 which as has been noted is a 30 volt DC battery in series with microswitch 64 and on-off switch 66. Microswitch 64 is actuatable concurrently with rotation of the core element 38 of valve means 32. It will be observed that when the valve means 32 is in the position illustrated in FIG. 2 there is no need for power to be supplied to the amplifier circuit since the stethoscope will operate as a standard stethoscope. Therefore, in this position switch 64 is opened by the valve means 32. However, rotation of knob 33 effects movement of core 38 of valve means 32 in order to align passageway 48 with the air column from hose 14 to the tube 50 and simultaneously closes microswitch 64. Similarly, switch 66 is coupled with volume control 32 of FIG. 1 which is further represented in FIG. 5 as potentiometer R11. The dashed line in FIG. 5 is indicative of the unison of movement between volume control 32 and switch 66. When volume control 32 is in the off position, switch 66 is open as shown in FIG. 5 and closed when volume control 32 is in the on position.

Therefore, with the valve means 32 as illustrated in the FIG. 4 position, switch 64 is closed and turning volume control 32 to the on position closes switch 66 thereby providing 30 volts DC to the electrical amplifier circuit, indicated generally at 30. The desired physiological sound such as a heart beat, is picked up at 12 and by means of a first acoustical transducer including a diaphragm in the pickup head 12 and the air column in hose 14, the sound is conveyed through tube 44, passageway 48 and tube 50 to cone 56 and then to a second acoustical transducer, microphone 58, which is on the input stage of the first stage of amplification for electrical amplifier circuit 30. Microphone 58 should be a high impedance device having a good response at low frequencies. One such device is manufactured by Shore of Evanston, Illinois, designated 99A405.

Specifically, the first stage of amplification includes a field effect transistor Q1. A field effect transistor is chosen because it has a high input impedance and approaches a vacuum tube in this regard. Specially, a 2N3088 field effect transistor is used.

The signal is applied to the first stage of amplification Q1 across an RC network consisting of capacitor C2 and resistors R3 and R2 in series with C2 and ground. A resistor R1 and C1 are in th e input stage of the first transistor amplifier with R1 forming a part of the biasing network together with resistor R2 for the field effect transistor Q1.

Transistors Q2, Q3, Q4 and Q5 are low noise transistors and are operated at low frequencies. Transistors Q2 through Q5 provide four additional stages of amplification for the physiological sound such as a heart beat. An input signal on the order of magnitude of to 12 millivolts peak to peak is received at the input stage. A gain of approximately 40 db is obtained in the stages of amplification Q1, Q2 and Q3. Q3 delivers an output through a volume control of potentiometer 32 also designated R11 and is RC coupled to the base of transistor Q4. As has already been noted, when the volume control potentiometer R11 is in the off position, switch 66 associated therewith is open as shown in FIG. 5.

The final two stages of amplification occur in transistors Q4 and Q5. It will be observed that varibale resistor R19 can be turned down to substantially zero ohms thereby effectively shorting capacitor C9 so as to obtain essentially flat amplification from a frequency range of 1 cycle per second to 20 kc., for example. With C9 shorted out, C8 becomes the only effective capacitor in the base circuit of the final stage of amplification through transistor Q5.

It is possible to supersede the input by means of an input jack indicated generally at 68 in FIG. 5. The jack is inserted so as to open normally closed contact 70 thereby making it possible to substitute and amplify any desired sound in the amplifier circuit 30 and listen to it by means of the earpieces 24, 26. Thus it is possible that a particular patients heartbeat may be compared with a known standard which may include the patients previously recorded heartbeat. This becomes very important for purposes in noting the changes which occur over a span of time and is also useful as a teaching device. Similarly, it is possible to take the output from two alternative sources from the final stage of amplification Q5. Normal practice is to take the amplified physiological sounds such as a heartbeat from the output of loudspeaker E1 designated 60 in FIGS. 2 and 4 and direct it through tube 54, passageway 57 into tube 52 and thereafter through flexible coupling 18 to the earpieces 24 and 26. However, it is possible to take the output and deliver it to any recording device such as an electrocardiogram, oscilloscope or a tape recorder. This is effected by inserting an output jack 72 thereby making the amplified signal available for any desired recording through jack 72.

Thus if it is desired to record the output signal on a central cardiogram a mixing circuit consisting of an attenuator, such as a 5 megohm potentiometer, may be electrically connected to jack 72.

It is also equally feasible to use the electronic stethoscope as a monitoring device, such as by a nurse, at a central station remote from the patient.

Operation of the amplifier circuit shown in FIG. 5 is believed to be apparent from the above description. The performance can be considered with respect to the illustrative circuit having components of the following types and values which has yielded a highly satisfactory electronic stethoscope. It will be apparent of course that the values and component types listed below are merely illustrative examples, and in no sense of the word should they be construed to be as limiting the instant invention.

R1330 kilohms C115 mfd. R2l30 kilohms C2l5 mfd. R3l megohm C3l00 mfd. R439 kilohms C4-l00 mfd. R527 kilohms C5.001 mfd. R6l00 ohms C6-100- mfd. R7133 kilohms C7l00 mfd. R847 kilohms R20270 ohms R9180 ohms C8-l00 mfd. R1010 kilohms C9-.2 mfd. R1110 kilohms C10100 mfd. R12-68 kilohms C11100 mfd. R13-100 kilohms C12-100 mfd. R143.3 kilohms Q12N3088 R15-8.2 kilohms Q22N930' R16-680 ohms Q3-2N930 R17100 ohms Q42N930 R18-1 kilohm Q5-2N1613 R1910 kilohms E12 kilohms Telex RTY04 Battery 30 volts DC The uses of the output from the electronic stethoscope are many and varied. For example, it is possible to take the output after it has been amplified and use it to trigger a digital counter so that an instant indication of the pulse rate may be obtained. When used in conjunction with a one shot multivibrator to produce a tone, for example one of approximately 1000 cycles per second, the doctor is given an audible indication that the patients heart beat is satisfactory while he feeds oxygen, takes blood pressure, palpitates the pulse on a patients neck, etc.

The advantages of the electronic stethoscope are also numerous. For example, the amplitude of low pitched heart tones and murmurs may be detected more easily, better detection of indistinct fetal heart beats caused by obesity or position of the fetus may be had, detection of pulmonary tones which may be difficult to hear because of chronic emphysema, or obesity. Better diagnostic advantages for the hard of hearing doctor. Provision of permanent record for case history by means of an attached recording device, as well as means for review by home study program course in cardiac ausculation.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention, the form hereinbefore described being merely a preferred embodiment thereof.

What is claimed is:

1. A combination electronic and air-column actuated stethoscope comprising:

(a) a pickup head including a mechanical-acoustical transducer adapted to monitor a physiological sound from a patients thorax,

(b) means defining a first air-column communicating with said mechanical-acoustical transducer,

(c) valve means for selectively directing said monitored physiological sound into one of a plurality of paths,

(d) an electronic input transducer mounted in one of said paths,

(e) means for electronically amplifiying said monitored physiological sound as it travels along at least one of said paths so as to obtain a substantially fiat amplification of the physiological sound being monitored,

(f) an electronic output transducer mounted in said one of said paths,

(g) means defining a second air-column for receiving the monitored physiological sound from said selectively directed paths,

(h) and a pair of ear pieces adapted to receive the monitored physiological sound from said second aircolumn,

(i) said valve means in one position thereof establishing a first passageway directly interconnecting in a straight through path, said first and second air columns whereby there is no interaction with said electronic input transducer and in a second position thereof establishing second and third passageways which interconnect respectively said first air column with said electronic input transducer and said electronic output transducer with said second air column.

2. A combination electronic and air-column actuated stethoscope as defined in claim 1 including a jack means for insertion of an additional signal into the input stage of said electronic amplifier circuit, and the elimination of said electronic input transducer from the electronic amplifier circuit, whereby any signal receivable at said input jack may be amplified in said electronic amplifier circuit and listened to in said pair of earpieces.

3. A combination electronic and air-column actuated stethoscope as defined in claim 1 including a jack means for receiving signals from the output stage of said electronic amplifier circuit,

whereby said amplified signals may be monitored at a location remote from said earpieces of said stethoscope.

4. A combination electronic and air-column actuated stethoscope as defined in claim 1 wherein said valve means comprises a fixed outer cylindrical sleeve member and a rotatable inner cylindrical member frictionally received in said fixed outer cylindrical sleeve member and said first passageway extends through said inner cylindrical member substantially normal to its longitudinal axis and said second passageway extends obliquely through said inner cylindrical member.

5. A combination electronic and air-column actuated stethoscope as defined in claim 1 wherein said first passageway in said valve means has a uniform inner diameter substantially equal to that of said first and second air columns to establish a substantially uninterrupted and uniform inner diameter from said pickup head to said earpieces whereby said combination stethoscope may operate solely as an air-column actuated stethoscope.

6. A combination electronic and air-column actuated stethoscope as defined in claim 1 wherein said valve means prevents actuation of said electronic input transducer and of said electronic output transducer when said first pas sageway of said valve means interconnects said first and second air columns whereby said combination stethoscope may operate solely as an air-column actuated stethoscope.

7. A combination electronic and air-column actuated stethoscope as defined in claim 1 including a first jack means for insertion of signals into the input stage of said electronic amplifier circuit,

and a second jack means for receiving said signals, as

amplified, from the output stage of said electronic amplifier,

whereby said amplified signals may be monitored at a location remote from said earpieces of said stethoscope.

8. A combination electronic and air-column actuated stethoscope as defined in claim 7 which permits simultaneous monitoring of two independent signals, one signal of which is directed through said air actuated stethoscope when said valve means is in said one position thereof whereby said first passageway is directly interconnected with said first and second air columns, and the second signal of which is directed through said electronic amplifier by means of said input jack to be amplified in said electronic amplifier and then received by said output jack,

whereby said amplified signal may be mointored at a location remote from said earpieces of said stethoscope.

References Cited UNITED STATES PATENTS 1,686,138 10/1928 Marvel 179-1 3,247,324 4/1966 Cefaly et al 179-1 3,182,129 5/1965 Clark et al 179-1 3,385,930 5/1968 Harshbarger 1791 WILLIAM C. COOPER, Primary Examiner R. P. MYERS, Assistant Examiner 

